This invention relates to a disk drive device used as an external memory unit of a computer system or the like.
There are various kinds of memory media of external memories or external memory units. Among the magnetic memories are floppy disks, hard disks (HDDs), and magnetic cards, and among optical memories are optical disks, magneto-optic disks and optical cards. In the category of semiconductor memories are semiconductor disks, IC cards, and IC memory cards. All those memory devices have no compatibility among them.
On the other hand, in the personal computers which are moving towards progressively lighter weight, there have been requirements for memory media with smaller size and larger capacity.
In the conventional technology, the kind of medium is selected according to the purpose of use, that is, where portability and replaceability are important, floppy disks, optical disks, and IC cards are selected, and where a large capacity is required, hard disks and optical disks are selected, and where small size and light weight are essential, IC cards are selected. However, if advantages of small size as small as the so-called card size and a large capacity are sought, the conventional external memories do not necessarily meet those requirements.